The present invention relates to a computer system adaptable to a personal computer, such as a notebook type personal computer, and more particularly to a computer system having a computer body and an expansion unit on which the computer body is detachably mounted.
The entire contents of Japanese Patent Application No. 8-71396 filed on Mar. 2, 1996 are incorporated herein by reference.
In recent years, a variety of portable computers, such as lap-top type personal computers and notebook type personal computers, have been developed, which can easily be carried by a user and which can be operated by a battery therein. In order to extend the function of a portable computer of the foregoing type, the portable computer is structured to be mounted on an expansion unit, if necessary.
The expansion unit has a drive bay for accommodating drive units, such as a hard disk drive, and extension slots for receiving a variety of option cards. Therefore, when the portable computer is connected to the expansion unit and operated when a requirement has arisen, the function of the portable computer can easily be extended while maintaining the portability of the portable computer. Recently, a major portion of the portable computers is adaptable to so-called hot docking with which addition (and deletion) of devices is permitted in a state where the system is being operated. The portable computer has been enabled to be mounted on the expansion unit during the operation of the system.
In recent years, a storage unit, such as a hard disk drive, having an access lock function has been developed. The access lock function is a function with which a predetermined password is previously stored in the hard disk drive so as to be subjected to a comparison with a password input from a user of the system when the system is booted and which permits an access only when the two passwords coincide with each other. As a result, even if the hard disk drive has been illegally removed and then mounted on another computer, leakage of stored information can previously be prevented.
As described above, the portable computer (the computer body) is mounted on the expansion unit if necessary to extend the function. In order to perform hot docking, the device in the expansion unit is, as a resource, assigned to the system during the operation of the system. Therefore, if a hard disk drive having the access lock function is accommodated in the expansion unit, a screen for releasing the access lock must be displayed on the computer body during the operation of the system.
In general, the operating system in the computer body has been operated when hot docking is performed, the operating system controlling the display and the keyboard.
Latest operating systems employ an interface called "GUI (Graphical User Interface). The GUI is arranged to display pictures and icons on the screen to permit a user to intuitively and easily use the computer such that the user uses a pointing device, such as a mouse, to instruct a displayed icon to perform a required operation. Therefore, for example, the control of the display on the display unit has a considerably complicated structure. Thus, a system BIOS cannot easily control the display during the operation of the operating system. If the system BIOS arbitrarily makes an access to the hardware such as the display unit, unconformity takes place over the system. As a result, the operating system is probable to be adversely affected.
Hitherto, if the storage device accommodated in the expansion unit is in the access lock state when hot docking has been performed, the system BIOS cannot therefore display the screen for inputting a password. Thus, the system BIOS cannot perform a process for releasing the access lock. Even if the screen for inputting a password can be displayed, return to the screen immediately before the screen for inputting a password is sometimes inhibited. Although the expansion unit is an important factor for extending the function of the portable computer as described above, the conventional structure cannot release the access lock of the storage device accommodated in the expansion unit when hot docking is performed. As a result, the storage device cannot be added as a resource for the portable computer.